Until relatively recently, the conventional method of butchering hogs does not contemplate the removal of the skin or skin prior to the butchering operations, but the hog, after killing, is passed through a series of operations designed to remove the hair and bristles and to thoroughly clean the outer skin surface of the hog carcass. In the conventional procedure, substantially all of the skin or skin remains on the hog during the killing operation and throughout most of the butchering operation.
In order to prepare the carcass for the conventional dehairing operation, the carcass is first scalded by placing it in a tank of hot water (at temperatures of from 135.degree. to 145.degree. F.) for about 5 minutes. The purpose of the scalding tank is simply to loosen up the hair of the hog to prepare the carcass for the dehairer. As is explained below, the hogs move through the slaughtering operation at speeds up to 3200 feet per hour, which requires a very large scalding tank. The installation of such a tank represents a substantial investment and the operation is costly in terms of the floor space required, the overall maintenance and the heat requirement necessary to keep the water at the requisite temperatures. Further, disposal of the water from the tank represents a serious pollution problem.
After the carcasses have been scalded in the tank, they are conveyed to a dehairing machine which comprises a series of rubber paddles which beat most of the loosened hair from the carcass. The dehairing machines are enormous machines which require a great deal of maintenance and consume large amounts of energy.
The next step in the conventional dressing method is to singe the carcass in a gas flame. The purpose of the gas flame is to burn off the remaining hair. In addition to requiring a substantial quantity of fuel, the fumes from the singeing apparatus are pungent and offensive, and represent another pollution problem. The operation of the dehairing and singeing equipment is extremely costly since the equipment required is expensive and requires substantial floor space, as well as requiring continuing maintenance. Further, since Federal regulations require that all equipment in packing houses be cleaned and sterilized on a daily basis, the maintenance of these machines requires a great deal of labor and consequently is very expensive.
Following the singeing operation, the carcasses are shaved to remove the last traces of hair and bristles. In some cases the bristles are sufficiently tough and embedded that portions of the skin or skin must be actually cut away. Since the carcasses vary in size substantially from one to another, it is necessary that the shaving operation be done by hand. In a typical operation, as many as eight men are required to carry out the shaving operation on a system designed to slaughter 1600 hogs per hour.
Following the shaving operation, the carcass is washed and is then ready for the butchering operation whereby the carcass is opened up. The conventional butchering operations which follow the cleaning of the skin include removal of the head, evisceration, splitting the carcass, and inspection of the carcass, which may take place in several stages.
Following the evisceration and splitting operations, in the conventional process, the split carcasses are chilled for a period of 12 to 20 hours in order to lower the internal carcass temperature to approximately 36.degree.-38.degree. F., the temperature necessary to firm up the meat and permit the carcass to be cut into primal cuts, after which various portions are skinned by a variety of methods, all of which involve labor and further expense. Eventually the whole carcass must be skinned which involves a great deal of manual labor. The scalding, singing and shaving operations reduce the value of the skin for use as leather, and the skin is usually relegated for use as gelatin or industrial grease.
In the butchering and dressing of hogs and other such animals, it is common to suspend the animals in the normal head-down position by their hind feet or legs by means of hooks or gambrels. The gambrels are swivelly mounted on trolleys located on carcass tracks which lead through the various butchering operations. The trolleys, and in turn the animals, are moved along the carcass track by a mechanism such as a chain conveyor having pusher plates attached to the chain, which plates push the trolleys about the killing and dressing rooms. In this manner, the animals are moved in a continuous stream to the stations in the plant where the various butchering operations are performed. In a hog butchering plant, the animals are typically hung on two foot centers, which leaves adequate space for the various butchering operations to be performed. To be commercially attractive, such plants must be capable of handling up to 1600 hogs per hour, so that it is desirable that the conveyor move at a maximum speed of up to 3200 feet per hour.
It is obviously desirable to dress as many carcasses as possible within a given period of time, since the unit cost to dress a given carcass will decrease with any increase in the number of carcasses dressed in any given period of time. It therefore follows that if the conveyor is stopped or slowed during any station of the operation, the total number of carcasses dressed in a given period of time will be decreased.
One of the operations in a packing plant which typically causes bottlenecks is the cleaning and dehairing operation.
Machinery has been devised in the prior art, described below, to remove the skin from a hog carcass in substantially one piece while the hog carcass is suspended or moving along a conveyor. In addition to eliminating the conventional scalding and dehairing operation and freeing up a significant amount of floor space in the plant, a skinning operation which does not scald, produces a skin which is a fine leather and is far more valuable than the skin from a scalded animal.
Most of these prior art patents describe the skinning of hogs while the carcasses are suspended in the normal head-down position by the hind legs, because the carcass is in the conventional head-down attitude for the sticking or bleeding operation. The prior art has simply left the carcass in the head-down attitude and devised various types of apparatus designed to skin the carcass while it was in this attitude. Examples of such prior art include U.S. Pat. No. 3,478,386 to Robison describes a non-continous skin puller apparatus which pulls the skin downwardly from the animal while the animal is suspended in the conventional head-down position.
Another example is U.S. Pat. No. 3,209,395 to Jones et al. Which teaches an apparatus for removing skin from animal carcasses wherein the carcass is suspended in the conventional head-down position and two shackles are used to pull the skin downwardly from the butt end to the head. At the present time no small volume slaughter plants are being built. The apparatus described by Jones, however, is not continuous and it is therefore not suitable for use in a high volume operation. Further, the Jones process requires extensive hand skinning of the carcass using ordinary knives or mechanical knives which results in scoring the skin, thus further reducing the value of the skin as leather. Further, the Jones apparatus appears to require the removed skin to be manually lifted from the up-turned hook to separate the skin from the apparatus. Still further, the Jones apparatus would appear to contaminate the carcass when the back of the carcass touches the chain 26 (shown in FIG. 14) as the skin is pulled from the carcass. Such an apparatus could not be used in a plant subject to USDA inspection.
Because it is difficult and heretofore has been considered impractical to skin a hog by drawing the skin from the butt toward the head, many prior art devices such as U.S. Pat. No. 3,423,789 to Ochylski and U.S. Pat. No. 3,621,514 to Brown accomplish the skinning by pulling the skin from the head end of the carcass toward the butt end of the carcass. In order to remove the skin from the carcass while the carcass is in the head-down position, it is necessary to secure the carcass, both by head and foot (butt-end or hind feet suspension), followed by drawing the skin from the head toward the butt in a substantially vertical, upward direction.
However, when hogs, or other animals enter a packing plant, their skins are normally covered with a substantial amount of dirt, loose hair, manure, and the like which has been picked up during transportation and storage in the stockyard pen and even though showered or mechanically scrubbed using equipment like a car wash, most loose hair and debris remain on the skin. If the animal is not dehaired and cleaned prior to the skinning operation, the dirt, hair and other contaminants on the skin have a tendency to fall onto the stripped carcass an embed on the fat of the carcass as the skin is being pulled upwardly. When the skin is finally freed from the carcass, the release is frequently accompanied by a shower of dirt, hair, fecal matter and other debris which falls around and onto the skinned carcass. This dirt becomes embedded in the fat of the carcass where it is very difficult to remove.
The USDA requires that all dirt, hair, fecal matter, or other contamination be removed from the skinned carcass before the carcass is further processed. All such foreign matter must be removed by cutting away the edible meat on which the fecal matter and other contaminants are found. Some prior art suggests that the foreign matter can be removed by washing or spraying, but that approach is not permitted by the USDA because high pressure sprays and showers can actually further imbed foreign particles in the fat or meat of the carcass and cause the fecal matter to further contaminate the meat as it is washed down the carcass. Thus, a hand operation to remove such foreign matter is still required. Removing the foreign matter from the carcass by hand is expensive and time consuming and results in some of the meat being trimmed away from the carcass, where it is relegated to non-edible uses. Thus, both clean up methods are suffer from many problems and are costly.